This invention relates to a labyrinth seal system for use in a centrifugal chemical processing pump or the like. More particularly, this invention relates to a labyrinth seal system including a rotating rotor driven by a pump shaft and an associated stationary stator.
In machines such as centrifugal pumps with rotating shafts, it is frequently necessary to obtain an effective seal between the rotating shaft and stationary element(s) of the machine. Rotating shaft seals may find particular application in bearing housings to prevent lubricants, used to lubricate bearing elements such as ball and thrust bearings, from leaking out of the housing. Another function of rotating shaft seals for bearing housings is to prevent contaminants, such as dirt, dust, water, pump leakage, and condensation, from entering the bearing housing.
The entrance of contaminants into a bearing housing can pose a threat to lubricating fluid therein. Should contaminants enter a bearing housing, lubrication of the bearings by the lubricating fluid (e.g. oil) can be substantially impaired. A loss of lubrication may cause bearings to operate at excessive temperatures, which can lead to premature failure of bearings and subsequent failure of the pump or other device that the bearing housing is incorporated into.
The escape of lubricants from a bearing housing through shaft seals is capable of causing similar problems. Frequent servicing may be required to replace escaping lubricants. Additionally, leakage of lubricating fluid from the bearing housing may cause an inadequate amount of lubricating fluid to remain in the housing such that excessive wear will take place on bearings and other components therein, and eventually leading to premature bearing failure.
One type of sealing device used to provide a seal about rotating shafts and particularly about shafts extending through bearing housings are mechanical labyrinth seals. Such seals commonly incorporate a rotating element or rotor and a stationary element or stator. In certain types of labyrinth seal, opposing faces of the stator and rotor are configured to form a maze or labyrinth flow along an interface between the rotor and stator. Opposing faces are machined to a tight tolerance so that the separation or gap between the opposing faces of the rotor and stator is narrow. The labyrinth path created by the labyrinth sealing element""s narrow separation inhibits the leakage of lubricants between the rotating rotor and stationary stator, and thus prevents them from leaving or passing through the seal. Similarly, the labyrinth inhibits the entrance of contaminants into a bearing housing or other structure through the rotor/stator created labyrinth. Exemplary labyrinth seals are disclosed, for example, in U.S. Pat. Nos. 5,316,317; 5,431,414; and 5,522,601, the disclosures of which are all hereby incorporated herein by reference.
The seals of the ""601 and ""414 patents have a rotating member which extends all the way to the outer extremities of the sealing device. Unfortunately, this makes it easy for maintenance personnel to accidently touch the rotating portion of the labyrinth seal and become injured. This, of course, is a disadvantage associated with the seals of these prior art patents.
Additionally, the seals of both the ""601 and ""414 patents incorporate a drain groove cut into the face of the stationary member. During assembly and installation, the rotating member is pushed up against the surface that this groove is recessed into. During initial wear-in of the seal, this groove in the surface scrapes away material from the surface of the rotating member and the removed material emerges as a fine dust. Some of this dust may be flung from the seal as it rotates, and additionally, some of the dust has been found to occasionally enter the internals of the equipment that is intended to be protected. This fine dust powder mixes with the oil and creates a mud-like slurry which contaminates the very oil or other lubricating fluid that it is intended to protect from contamination. These, of course, are serious disadvantages with the seals of the ""601 and ""414 patents.
As can be seen from the above, there exists a need in the art for an improved labyrinth type seal for protecting bearing housings or other structures from contamination.
It is a purpose of this invention to fulfill the above-described needs in the art, as well as other needs apparent to the skilled artisan from the following detailed description of this invention.
An object of this invention is to provide an improved labyrinth seal for use in centrifugal pumps and other mechanical equipment.
Another object of this invention is to provide a labyrinth seal which eliminates rotating surfaces from rubbing directly against grooved surfaces thereby eliminating the scraping of material from rotating surfaces. Generation of fine powder from such scraping is thus reduced or even substantially eliminated.
Another object of this invention is to provide a labyrinth seal design which incorporates a stationary covering over the outer surface of the rotating member making maintenance personnel less susceptible to injury.
Yet another object of this invention is to provide a labyrinth seal design which does not require a heat process for assembly, and thus allows for reduced manufacturing costs and less potential complications.
Still another object of this invention is to provide a labyrinth seal which includes an annular radial trap groove-type system which enhances performance of the seal. This radial trap may be an annular groove between the rotating and stationary members. A portion of this groove (e.g. half) may be formed by a recess or cutout in the face of the stationary member and the other portion of the groove may be formed by an opposite recess or cutout in the face of the rotating member. Contamination which traverses radially inward through the tight clearance between these parts will enter this groove area. Since the groove area is of wider clearance, the path of least resistance for the contamination becomes this groove which directs the contamination circumferentially around the shaft to a position (e.g. six o""clock position) where it simply drains back out of the assembly via a drainage cutout or notch.
This invention will now be described with respect to certain embodiments thereof, along with reference to the accompanying illustrations.